Composite compact articles comprising a cluster of abrasive particles bonded to a support medium are known in the art. These are widely useful in a variety of industrial applications, such as shaping, extruding, cutting, abrading, drilling, and the like.
Special mention is made of abrasive particle clusters comprising diamond, cubic boron nitride (CBN), wurtzite boron nitride (WBN) or mixtures of any of the foregoing. These are known to possess very good abrasion and wear-resistance properties. Clusters of this type can be made by following procedures in the patent literature, e.g., Bovenkerk, U.S. Pat. No. 3,136,615, Wentorf, Jr., U.S. Pat. No. 3,609,818 and Wentorf, Jr., et al, U.S. Pat. No. 3,233,988, incorporated herein by reference.
Such abrasive particle clusters are made into composite compact articles by bonding the cluster to a metal or cemented tungsten carbide support, usually under conditions of temperature and pressure at which the abrasive particles are crystallographically stable. Such particles are commercially available and methods of preparation are described in the patent literature, e.g., Wentorf, Jr. and Rocco, U.S. Pat. No. 3,745,623 and U.S. Pat. No. 3,743,489 and Mitchell, U.S. Pat. No. 4,063,909, which are incorporated herein by reference.
Tools made with the composite compact are manufactured in the usual case by brazing a surface of the support portion of the compact to a surface of a steel tool shank or indexable type insert made either from steel or tungsten carbide. This bonding may be achieved by means of a low temperature braze, e.g., at a temperature of about 700.degree. C. or lower. Such brazing, however, is not always satisfactory because the bond strengths are insufficient for certain commercial applications.
Brazing at higher temperatures, on the other hand, although resulting in higher bond strengths, sometimes approaches or exceeds temperatures at which the abrasive particles are thermally unstable. Using conventional high temperature brazing methods, it is often difficult to prevent the decomposition of at least some of the abrasive particles without taking special precautions.
There has now been discovered a method of joining composite compacts of abrasive particles to tool parts without subjecting the abrasive particles to elevated temperatures significantly above ambient. Bond strengths comparable to those of conventional brazing are achieved. Moreover, after the procedure has been completed, depending upon the conditions employed, substantially no brazing material can be caused to remain between the joined surfaces as a region of low resistance susceptible to erosion-type failure during normal use.